Aptamer-functionalized GSTK1-derived Super-Mito-EV enable targeted mitochondrial restoration for intervertebral disc repair

The progression of intervertebral disc degeneration (IDD) is accompanied by mitochondrial dysfunction and ferroptosis in nucleus pulposus cells (NPCs), highlighting the need for further investigation into mitochondrial homeostasis-related mechanisms and targeted therapeutic strategies. We found that the mitochondrial protein GSTK1 is downregulated in degenerative NPCs, whereas its overexpression partially delays IDD progression in rats. Mechanistically, the GSTK1-ALDH1L2 axis exerts anti-ferroptotic effects by maintaining mitochondrial homeostasis, independently of the classical ACSL4 pathway. GSTK1 also promotes the formation of mitochondria-containing extracellular vesicles through CD38/IP3R/Ca 2+ -associated signaling. Based on these findings, we generated mitochondria-enriched extracellular vesicles derived from GSTK1-overexpressing NPCs (Super-Mito-EV), modified them with EY3 to enhance targeted mitochondrial transfer, and incorporated them into a thermosensitive hydrogel to construct an injectable sustained-release delivery system. In a rat IDD model, this strategy significantly delayed IDD and improved disc structure and molecular homeostasis. In summary, our findings reveal the role of GSTK1–ALDH1L2-mediated mitochondrial homeostasis in IDD-associated ferroptosis and propose a targeted therapeutic strategy based on Super-Mito-EV-mediated mitochondrial delivery.